1. Field of the Invention
This invention relates to a method and an apparatus for generating raster lines for displaying multiple images on a single film sheet and more particularly, to a method and an apparatus for generating raster lines that include both image and image border information.
2. Description of the Prior Art
In the medical diagnostic imaging environment it is often desirable to combine and display a number of images representing different views of a given subject on a single sheet for review by a physician. The images may originate from various sources such as CAT-scans, NMR, radiography etc. and kept in a library of images in digital format. The images may be of different sizes and formats. An appropriate technology for formatting such images in an optimal way as to most efficiently use the available display area is disclosed in copending application Ser. No. 07/692,654, filed Apr. 29, 1991 in the names of Faulhaber and Taylor (IM-0406), now U.S. Pat. No. 5,214,519, and assigned to the assignee of the present application. This last-mentioned application describes a method and apparatus for capturing and displaying multiple medical diagnostic images stored in digital form on a single sheet of, typically, photographic film.
In order to operate at high speeds and to tie up a computer network as briefly as possible, information for each image is transmitted to a dedicated printer, often referred in the medical diagnostic field as a "camera", for generating a hard copy for study. The information is usually transmitted in serial format over a communication network and is received by the printer and stored in a memory, without undergoing any mapping process. The printer is able to receive and store enough information to produce a complete sheet. The information received typically includes, in addition to actual image data, instructions for image layout and display, instructions regarding border and if desired line framing.
The hard copy is produced in the camera by exposing a photosensitive film sheet in a laser type scanner, in raster fashion with information contained in the printer memory. In displaying the images, it is highly desirable to provide distinct borders separating each image from the background. Since the information in the memory is not provided in a format ready for raster display, a rasterization process must occur in the printer prior to the printing of the images. This rasterization process must obtain information both from different image sources and from border instructions and supply the appropriate exposure commands for each line, pixel by pixel to the film exposure device. i.e. a laser beam. It is highly desirable to effectuate such rasterization as rapidly as possible with minimal computation, preferably in hardware, and to produce a visually pleasing display, especially one in which the images are visually readily distinguished from background areas such as borders, so as not to confuse the observer.